Papers by Keyword: Boiler Tube

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Authors: Shahida Begum, A.N. Mustafizul Karim, Mohamed Ansari M. Nainar, Sukhana Sevah
Abstract: Boiler tube failures usually result in frequent forced outages, and ultimately in costly extended outages for major tubing replacement in a plant. There are several failure modes that may occur in a boiler tube, i.e. stress-corrosion cracking, pitting, water-side corrosion, fire-side corrosion, fatigue failure, overheating, dissimilar metal weld fatigue, mechanical fatigue and erosion. In this research the failure modes of boiler and its end cracks due to the dissimilar metal weld is analyzed. Hence data are collected and explored to determine the cause of failure and as a solution ceramic ferrule is suggested. The use of ceramic ferrule in boiler tube can eliminate the crack occurrence or delay the process due to thermal properties. The prevention of crack will reduce frequent maintenance and thus the cost of operation can be minimized.
Authors: J.Z. Hu, Shi Ning Ma, X.R. Chen
Abstract: A new novel cored wire for producing FeCrAl/WC intermetallic coating by arc spraying was developed. The erosion wastage at high temperature of the coating was researched with different impingement angles and temperatures. The results indicated that impingement angle and temperature greatly affected erosion wastage of the coating. At the same time, when impingement angle was 90°, different temperature had a little effect on the erosion wastage. And when temperature was 650°C, different impingement angle had a little effect on the erosion wastage too. As compared with water wall tube material (G20 steel) of power station boiler, the erosion resistance at high temperature of the coating was higher. The erosion resistance rate of the coating was 1.94~2.89 times of that of G20 steel when temperature was 650°C and particle was polygonal silica. The results indicated that erosive condition of high temperature flue gas and fly ash mixture in boiler tube of pulverized coal fired power station could be solved with the FeCrAl/WC coating.
Authors: Cukup Mulyana, Aswad Hi Saad, Mariah Kartawidjaja, Agtri Henboral
Abstract: Critical component of boiler that frequently experiencing failure is on the junction of boiler tube consist of two different materials. This failure mechanism would lead to tube rupture and would be followed by power plant shutdown. Failure analysis has been conducted on dissimilar metal weld (DMW) of Ferritic SA-213 T22 welded with Austenitic SA-213 TP 304H. This tube is used in Suralaya Steam Power Plant. Operating temperature and pressure of the steam inside the tube in normal condition are respectively 196.8kg/cm2 and 540 °C.In order to understand the real cause of failure several tests are ran, which are chemical composition test, micro vickers, and metallographic test on based metal, heat effective zone, and filler area. The tests are conducted in a layered manner to clearly understand the cause of the failure. Causes of the failure are due to the contribution of carbon diffusion and disparity of expansion coefficient of two materials.
Authors: Shahida Begum, A.N. Mustafizul Karim, M.A Shafii
Abstract: Boiler is a closed vessel in which the water is heated up to convert it from the liquid phase to superheat steam at specified pressure by addition of heat. The tubes are operated continuously at high temperature due to the formation of scale which has lower conductivity than that of steel. The scale can be formed for various reasons of which tube geometries, flue gas and steam temperature are prominent. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes. In this investigation an iterative technique was used to determine the temperature distribution across the tube with the increase of operating time. The operating time was considered up to 160,000 hours. The remaining life of the steam generator tube was found by finding hoop stress and Larson Miller Parameter from the Larson Miller Parameter curve for SA213-T22 material. The remaining life of the steam generator tube was used to find cumulative creep damage. By utilizing finite element modelling software, ANSYS 9/ ANSYS 11 the temperature distribution across the steam generator tube was evaluated. The temperature distribution along with Larson Miller Parameter predicted the oxide scale thickness. It was also observed that different input parameters have pronounced affect on the formation of oxide scale inside the steam generator tube. By increasing the heat transfer rate across the wall, the oxide scale thickness was increased more rapidly than normal condition. It was also observed that due to formation of scale the thermal conductivity in the boiler tubes was affected and the remaining life of boiler tubes was decreased and accelerated creep damage.
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